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Very low energy STEM for biology
Frank, Luděk ; Nebesářová, Jana ; Vancová, Marie ; Paták, Aleš ; Müllerová, Ilona
Examination of tissue sections with transmitted electrons has been performed at energies of hundreds and tens of eV with thicknesses of sections of 10 nm or less. This was possible by employing the cathode lens principle working without lowest energy limitations with the help of biasing the sample to a high negative potential. The reflected and transmitted electrons were attracted with the same electric field to earthed detectors situated above and below the sample. Very high image contrasts have been obtained even for samples free of any heavy metal salts for contrast enhancement.
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Electron vortex beam
Müllerová, Ilona ; Řiháček, Tomáš
Vortex electromagnetic waves contain a phase singularity along their propagation direction and are formed by the spiralling wave fronts that give rise to angular momentum in that direction. Vortex photon beams are widely used optical tweezers to manipulate micrometre-sized perticles, as optical micro motors etc.
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Influence of annealing to stress in CNx:(H) films observed by SLEEM
Mikmeková, Eliška ; Mikmeková, Šárka ; Müllerová, Ilona ; Sobota, Jaroslav
The effect of high residual stress on the quality of thin sputtered carbon nitride films has been studied by Scanning Low Energy Electron Microscopy (SLEEM). Basically, two different types of stress can be identified in thin films: compressive stress and tensile stress. Compressive stress leads to wrinkling and film delamination and tensile stress can cause the fracturing of thin films. Experiments were made in the Tescan TS 5130 MM equipped with the Cathode Lens system (CL), which enable us to observe samples at arbitrary landing energies of the illuminating electrons. Operating of a SEM at low energies offers several advantages: an increase of materials contrast via low energy, high ratio SE, BSE signal and noise, smaller interaction volume and elimination of charging effects. The effect of annealing in vacuum to residual stress (calculated from Stoney’s equation) was measured. The porous character of films was observed by thermal desorption spectroscopy (TDS).
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Characterization of industrial materials by slow and very slow electrons
Mikmeková, Šárka ; Müllerová, Ilona ; Frank, Luděk
Progress in materials science and engineering is inseparably connected with excellent knowledge of the correlation between materials properties and their microstructure. In our experiment an ultra-high vacuum scaning low energy electron microscope (UHV SLEEM) of an in-house design was used to observe microstructure of specimens. The UHV SLEEM is equipped with the cathode lens (CL) assembly, which enables us to observe samples at arbitrary landing energies of primary electrons. The device provides argon ion beam for in-situ cleaning of the specimen surface.
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Observation of high stressed hydrogenated carbon nitride films by SLEEM
Mikmeková, Eliška ; Müllerová, Ilona ; Sobota, Jaroslav
Two main factors can lead to losing adhesion in thin sputtered carbon nitride films: high residual stress and absorption of humidity. Basically, two different types of stress can be identified in thin films: compressive stress and tensile stress. Compressive stress can lead to wrinkling and film delamination, and tensile stress can cause the fracturing of thin films. For reactive sputtering of hydrogenated carbon nitride films, the compressive stress is typical. The films were prepared from graphite target (high purity, 99.9999 %) in mixture of nitrogen and hydrogen discharge.
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Surface crystallinity at the sight of electrons
Frank, Luděk ; Mikmeková, Šárka ; Mika, Filip ; Müllerová, Ilona
Scattering of electrons, injected into solids in order to produce an electron optical image of their surfaces, is governed by inner potentional of the sample with its spatial distribution inherent to the target structure. Except truly amorphous materials of the spatial arrangement range shorter than the interaction volume of electrons, we meet anisotropic scattering with the resulting image signal responding to the local crystalline structure. Incident electrons undergo scattering events the number of wich depends on their energy and on the scattering cross section of the material and the final emitted current results from statistics of these events.
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